Hitherto, the method of finding the internal resistance of an object of measurement by continuously changing a voltage in accordance with time within a fixed range and measuring a current to evaluate the electrochemical characteristic of the object of measurement including a fuel cell, a secondary battery, and so forth has been performed (see Patent Document 1, for example).
Further, the method of executing measurement by waiting until a voltage is stabilized while changing a load in stages by hand has been performed.
Further, cyclic voltammetry which is widely used for the study of the oxidation-reduction potential of a substance in solution, an electrode substance, etc. and/or an electrode reaction mechanism (the charge transfer, an associated chemical reaction, adsorption, etc.) has been known. The cyclic voltammetry is performed by reciprocally executing the potential scan. In the case where the cyclic voltammetry is performed, a correct measurement cannot be made unless conditions are not met, where the conditions include being under no influence of convection because an electrode and/or solution remains at rest, being under no influence of migration because a supporting electrolyte dissolves and ionizes sufficiently, using a plane electrode so that a linear diffusion pattern is achieved, no reactant deposited on an electrode and occurrence of no chemical reaction, the electron transfer being reversible, and so forth. (see Non-Patent Document 1, for example).
On the other hand, next-generation fuel cells including a biofuel cell, a fuel cell using liquid fuel, and so forth have been developed. The biofuel cell includes an enzyme fuel cell using an enzyme for an electrode, a microbial fuel cell using a microorganism for an electrode, and so forth. The enzyme fuel cell is a fuel cell generating power through the oxidation-reduction enzyme of an electrode.
Further, the fuel cell using the liquid fuel denotes a fuel cell that uses an inorganic catalyst (e.g., platinum) for an anode and that uses liquid fuel including methanol, ethanol, etc. The liquid fuel has higher molecular weight and high energy density. However, the reactivity of the liquid fuel is rather low.
Particularly, the microbial fuel cell expected to be a next-generation type bioenergy recovery process can directly produce electric energy from biomass through biochemical conversion. It has been expected that the use of the device allows for eliminating energy losses occurring when fuel generated through the methane fermentation and/or the hydrogen fermentation is converted through the use of a power generator. (See Patent Document 2, for example.)
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2007-66590 (the eighth page)
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2007-227216
[Non-Patent Document 1] The Electrochemical Society Ed. “Electrochemical Measurement Manual Basic version”, Maruzen Company, Limited, April in 2002, p. 94